Communications system, communications device and method

ABSTRACT

A method of allocating resources for communications in a mobile telecommunication system wherein the mobile telecommunication system includes a wireless interface for a base station to communicate with communications devices and wherein a communications device is operable to transmit signals to another communications device using resources of the wireless interface and in accordance with a device-to-device communication protocol. A first pool of the resources is allocated to device-to-device communications of broadcast type and a second pool of the resources is allocated to a device-to-device communications of unicast type, the second pool of resources being separate from the first pool. The method includes a first communications device transmitting broadcast messages using resources of the first resources pool and a second communications device transmitting unicast messages using resources of the second resources pool.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 15/502,013, filed Feb. 6, 2017, which is based onPCT filing PCT/EP2015/070773, filed Sep. 10, 2015, and claims priorityto European Patent Application 14184600.6, filed in the European PatentOffice on Sep. 12, 2014 the entire contents acacia of which beingincorporated herein by reference.

TECHNICAL FIELD OF THE DISCLOSURE

The present disclosure relates to communications systems fordevice-to-device communication, communications devices fordevice-to-device communication and methods of allocating resources.

BACKGROUND OF THE DISCLOSURE

Mobile telecommunication systems, such as those based on the 3GPPdefined UMTS and Long Term Evolution (LTE) architecture, are able tosupport more sophisticated services than simple voice and messagingservices offered by previous generations of mobile telecommunicationsystems. For example, with the improved radio interface and enhanceddata rates provided by LTE systems, a user is able to enjoy high datarate applications such as video streaming and video conferencing onmobile communications devices that would previously only have beenavailable via a fixed line data connection.

The demand to deploy fourth generation networks is therefore strong andthe coverage area of these networks, i.e. geographic locations whereaccess to the networks is possible, is expected to increase rapidly.However, although the coverage and capacity of fourth generationnetworks is expected to significantly exceed those of previousgenerations of communications networks, there are still limitations onnetwork capacity and the geographical areas that can be served by suchnetworks. These limitations may, for example, be particularly relevantin situations in which networks are experiencing high load and high-datarate communications between communications devices, or whencommunications between communications devices are required but thecommunications devices may not be within the coverage area of a network.In order to address these limitations, in LTE release-12 the ability forLTE communications devices to perform device-to-device (D2D)communications will be introduced.

D2D communications allow communications devices that are in closeproximity to directly communicate with each other, both when within andwhen outside of a coverage area or when the network fails. This D2Dcommunications ability can allow user data to be more efficientlycommunicated between communications devices by obviating the need foruser data to be relayed by a network entity such as a base station, andalso allows communications devices that are in close proximity tocommunicate with one another although they may not be within thecoverage area of a network. The ability for communications devices tooperate both inside and outside of coverage areas makes LTE systems thatincorporate D2D capabilities well suited to applications such as publicsafety communications, for example. Public safety communications requirea high degree of robustness whereby devices can continue to communicatewith one another in congested networks and when outside a coverage area.

Fourth generation networks have therefore been proposed as a costeffective solution to public safety communications compared to dedicatedsystems such as TETRA, which are currently used throughout the world.However the requirements and expectations for public safetycommunications can differ from those for conventional LTEcommunications. In particular, the technical constraints of publicsafety D2D communications can thus create challenges for other D2Dcommunications, for example for non-public safety communications. Inparticular, D2D communications are well suited for direct one-to-many(broadcast) communications but not well suited to one-to-one (unicast)communications.

SUMMARY OF THE DISCLOSURE

According to a first aspect of the invention, there is provided a methodof allocating resources for communications in a mobile telecommunicationsystem wherein the mobile telecommunication system provides a wirelessinterface for a base station to communicate with communications devicesand wherein a communications device is operable to transmit signals toanother communications device using resources of the wireless interfaceand in accordance with a device-to-device communication protocol. Afirst pool of the resources is allocated to device-to-devicecommunications of the broadcast type and a second pool of the resourcesis allocated to a device-to-device communications of the unicast type,the second pool of resources being separate from the first pool. Themethod comprises a first communications device transmitting broadcastmessages using resources of the first resources pool; and a secondcommunications device transmitting unicast messages using resources ofthe second resources pool. In other words, there is provided a methodwhich comprises transmitting broadcast device-to-device messages usingresources of a resources pool and transmitting unicast device-to-devicemessages using resources of a different resources pool.

According to another aspect of the present invention there is provided amobile telecommunication system for device-to-device communication. Themobile telecommunication system comprises a base station; andcommunications devices. The mobile telecommunication system provides awireless interface for the base station to communicate with thecommunications devices. One of the communications devices is operable totransmit signals to another one of the communications devices usingresources of the wireless interface and in accordance with adevice-to-device communication protocol. A first pool of the resourcesis allocated to device-to-device communications of the broadcast typeand a second pool of the resources is allocated to a device-to-devicecommunications of the unicast type, the second pool of resources beingseparate from the first pool. A first of the communications devices isconfigured to transmit broadcast messages using resources of the firstresources pool; and a second of the communications devices is configuredto transmit unicast messages using resources of the second resourcespool.

According to a further aspect of the present invention, there isprovided a communications device for device-to-device communication,wherein the communication device is configured to operate in a mobiletelecommunication system, the mobile telecommunication system providinga wireless interface for a base station to communicate withcommunications devices. The communications device is operable totransmit signals to another communications device using resources of thewireless interface and in accordance with a device-to-devicecommunication protocol. The communications device being operable totransmit signals in accordance with a device-to-device communicationprotocol comprises the communications device being operable to transmitbroadcast messages using resources of a first pool of resources; and thecommunications device being operable to transmit unicast messages usingresources of a second pool of resources, the second pool of resourcesbeing separate from the first pool of resources.

Various further aspects and features of the present disclosure aredefined in the appended claims and include a communications device, amethod of communicating using a communications device.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample only with reference to the accompanying drawings wherein likeparts are provided with corresponding reference numerals and in which:

FIG. 1 provides a schematic diagram of a mobile communications system;

FIG. 2 provides a schematic diagram of the structure of a downlink of awireless access interface of a mobile communications system;

FIG. 3 provides a schematic diagram of an uplink of a wireless accessinterface of a mobile communications system;

FIG. 4 provides a schematic diagram of a mobile communications system inwhich communications devices can perform device-to-devicecommunications;

FIGS. 5a to 5d provides schematics diagrams of example device-to-devicecommunications scenarios;

FIG. 6 provides a schematic illustration of a UE;

FIGS. 7A-7C provide an illustration of an example of resources poolallocation in accordance with the present disclosure;

FIG. 8 provides examples of an example of resources pool illustrationsin accordance with the present disclosure;

FIG. 9 provides an example of grouping within a resources pool inaccordance with the present invention;

FIG. 10 provides an example use case for 1:1 D2D communications;

FIG. 11 provides an illustration of an example of dedicated resourcesallocations based on sources in accordance with the present disclosure;

FIG. 12 provides another illustration of an example of dedicatedresources allocations based on destinations in accordance with thepresent disclosure;

FIGS. 13A-13B provide an illustration of an example of dedicatedresources allocations based on sources and destinations in accordancewith the preset disclosure;

FIG. 14 provides an illustration of an example of dedicated resourcesallocations based on a source-destination pair;

FIG. 15 provides an illustration of an example of resources allocationscontrolled by a terminal in accordance with the present disclosure;

FIG. 16 provides an illustration of an example of resources allocationscontrolled by a base station in accordance with the present disclosure;

FIG. 17 provides another illustration of another example of resourcesallocations controlled by a base station in accordance with the presentdisclosure;

FIG. 18 provides an illustration of an example of a resources allocationand data two-way exchange in accordance with the present disclosure; and

FIG. 19 provides an illustration of another example of a resourcesallocation and data two-way exchange an accordance with the presentdisclosure.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 provides a schematic diagram of a conventional mobiletelecommunications system 100, where the system includes mobilecommunications devices 101, infrastructure equipment 102 and a corenetwork 103. The infrastructure equipment may also be referred to as abase station, network element, enhanced Node B (eNodeB or eNB) or acoordinating entity for example, and provides a wireless accessinterface to the one or more communications devices within a coveragearea or cell. The one or more mobile communications devices maycommunicate data via the transmission and reception of signalsrepresenting data using the wireless access interface. The networkentity 102 is communicatively linked to the core network 103 where thecore network may be connected to one or more other communicationssystems or networks which have a similar structure to that formed fromcommunications devices 101 and infrastructure equipment 102. The corenetwork may also provide functionality including authentication,mobility management, charging and so on for the communications devicesserved by the network entity. The mobile communications devices of FIG.1 may also be referred to as communications terminals, user equipment(UE), terminal devices and so forth, and are configured to communicatewith at least one or more other communications devices served by thesame or a different coverage area via the network entity. Thesecommunications may be performed by transmitting and receiving signalsrepresenting data using the wireless access interface over the two waycommunications links resented by lines 104 to 109, where 104, 106 and108 represent downlink communications from the network entity to thecommunications devices and 105, 107 and 109 represent the uplinkcommunications from the communications devices to the network entity.The communications system 100 may operate in accordance with any knownprotocol, for instance in some examples the system 100 may operate inaccordance with the 3GPP Long Term Evolution (LTE) standard where thenetwork entity and communications devices are commonly referred to aseNodeB and UEs, respectively.

FIG. 2 provides a simplified schematic diagram of the structure of adownlink of a wireless access interface that may be provided by or inassociation with the eNodeB of FIG. 1 when the communications system isoperating in accordance with the LTE standard. In LTE systems thewireless access interface of the downlink from an eNodeB to a UE isbased upon an orthogonal frequency division multiplexing (OFDM) accessradio interface. In an OFDM interface the resources oldie availablebandwidth are divided in frequency into a plurality of orthogonalsubcarriers and data is transmitted in parallel on a plurality oforthogonal subcarriers, where bandwidths between 1.25 MHZ and 20 MHzbandwidth may be divided into 128 to 2048 orthogonal subcarriers forexample. Each subcarrier bandwidth may take any value but in LTE it isfixed at 15 KHz. As shown in FIG. 2 the resources of the wireless accessinterface are also temporally divided into frames where a frame 200lasts 10 ms and is subdivided into 10 subframes 201 each with a durationof 1 ms. Each subframe is formed from 14 OFDM symbols and is dividedinto two slots each of which comprise six or seven OFDM symbolsdepending on whether a normal or extended cyclic prefix is beingutilised between OFDM symbols for the reduction of intersymbolinterference. The resources within a slot may be divided into resourcesblocks 203 each comprising 12 subcarriers for the duration of one slotand the resources blocks farther divided into resource elements 204which span one subcarrier for one OFDM symbol, where each rectangle 204represents a resource element.

In the simplified structure of the downlink of an LTE wireless accessinterface of FIG. 2, each subframe 201 comprises a control region 205for the transmission of control data, a data region 206 for thetransmission of user data, reference signals 207 and synchronisationsignals which are interspersed in the control and data regions inaccordance with a predetermined pattern. The control region 205 maycontain a number of physical channels for the transmission of controldata, such as a physical downlink control channel (PDCCH), a physicalcontrol format indicator channel (PCFICH) and a physical HARQ indicatorchannel (PHICH). The data region 206 may contain a member of physicalchannel for the transmission of data, such as a physical downlink sharedchannel (PDSCH) and a physical broadcast channels (PBCH). Although thesephysical channels provide a wide range of functionality to LTE systems,in terms of resource allocation and the present disclosure PDCCH andPDSCH are mast relevant. Further information on the structure andfunctioning of the physical channels of LTE systems can be found in[11].

Resources within the PDSCH may be allocated by an eNodeB to UEs beingserved b the eNodeB. For example, a number of resource blocks of thePDSCH may be allocated to a UE in order that it may receive data that ithas previously requested or data which is being pushed to it by theeNodeB, such as radio resource control (RRC) signalling. In FIG. 2 UE1has been allocated resources 208 of the data region 206, UE2 resources209 and UE resources 210. UEs in an LTE system may be allocated afraction of the available resources of the PDSCH and therefore UEs arerequired to be informed of the location of their allocated resourceswithin the PDCSH so that only relevant data within the PDSCH is detectedand estimated. In order to inform the UEs of the location of theirallocated communications resources, resource control informationspecifying downlink resource allocations is conveyed across the PDCCH ina form termed downlink control information (DCI), where resourceallocations for a PDSCH are communicated in a preceding PDCCH instancein the same subframe. During a resource allocation procedure, UEs thusmonitor the PDCCH for DCI addressed to them and once such a DCI isdetected, receive the DCI and detect and estimate the data from therelevant part of the PDSCSH.

FIG. 3 provides a simplified schematic diagram of the structure of anuplink of an LTE wireless access interface that may be provided by or inassociation with the eNodeB FIG. 1. In LTE networks the uplink wirelessaccess interface is based upon a single easier frequency divisionmultiplexing FDM (SC-FDM) interface and downlink and uplink wirelessaccess interfaces may be provided by frequency division duplexing (FDD)or time division duplexing (TDD), where in TDD implementations subframesswitch between uplink and downlink subframes in accordance withpredefined patterns. However, regardless of the form of duplexing used,a common uplink frame structure is utilised. The simplified structure ofFIG. 3 illustrates such an uplink frame in an FDD implementation. Aframe 300 is divided in to 10 subframes 301 of 1 ms duration where eachsubframe 301 comprises two slots 302 of 0.5 ms duration. Each slot isthen formed from seven OFDM symbols 303 where a cyclic prefix 304 isinserted between each symbol in a manger equivalent to that in downlinksubframes. In FIG. 3 a normal cyclic prefix is used and therefore thereare seven OFDM symbols within a subframe, however, if an extended cyclicprefix were to be used, each slot would contain only six OFDM symbols.The resources of the uplink subframes are also divided into resourceblocks and resource elements in a similar manner to downlink subframes.

Each uplink subframe may include a plurality of different channels, forexample a physical uplink shared channel (PUSCH) 305, a physical uplinkcontrol channel (PUCCH) 306, and a physical random access channel(PRACH). The physical Uplink Control Channel (PUCCH) may carry controlinformation such as ACK/NACK to the eNodeB for downlink transmissions,scheduling request indicators (SRI) for UEs wishing to be scheduleduplink resources, and feedback of downlink channel state information(CSI) for example. The PUSCH may carry UE uplink data or some uplinkcontrol data. Resources of the PUSCH are granted via PDCCH, such a grainbeing typically triggered by communicating to the network the amount ofdata ready to be transmitted in a buffer at the UE. The PRACH may bescheduled in any of the resources of an uplink frame in accordance witha one of a plurality of PRACH patterns that may be signaled to UE indownlink signalling such as system information blocks. As well asphysical uplink channels, uplink subframes may also include referencesignals. For example, demodulation reference signals (DMRS) 307 andsounding reference signals (SRS) 308 may be present in an uplinksubframe where the DMRS occupy the fourth symbol of a slot in whichPUSCH is transmitted and are used for decoding of PUCCH and PUSCH data,and where SRS are used for uplink channel estimation at the eNodeB.Further information on the structure and functioning of the physicalchannels of LTE systems can be found in [1].

In an analogous manner to the resources of the PDSCH, resources of thePUSCH are required to be scheduled or granted by the serving eNodeB andthus if data is to be transmitted by a UE, resources of the PUSCH arerequired to be granted to the UE by the eNodeB. At a UE, PUSCH resourceallocation is achieved by the transmission of a scheduling request or abuffer status report to its serving eNodeB. The scheduling request maybe made, when there is insufficient uplink resource for the UE to send abuffer status report, via the transmission of Uplink Control Information(UCI) on the PUCCH when there is no existing PUSCH allocation for theUE, or by transmission directly on the PUSCH when there is an existingPUSCH allocation for the UE. In response to a scheduling request, theeNodeB is configured to allocate a portion of the PUSCH resource to therequesting UE sufficient for transferring a buffer status report andthen inform the UE of the buffer status report resource allocation via aDCI in the PDCCH. Once or if the UE has PUSCH resource adequate to senda buffer status report, the buffer status report is sent to the eNodeBand gives the eNodeB information regarding the amount of data in anuplink buffer or buffers at the UE. After receiving the buffer statusreport, the eNodeB can allocate a portion of the PUSCH resources to thesending UE in order to transmit some of its buffered uplink data andthen inform the UE of the resource allocation via a DCI in the PDCCH.For example, presuming a UE has a connection with the eNodeB, the UEwill first transmit a PUSCH resource request in the PUCCH in the form ofa UCI. The UE will then monitor the PDCCH for an appropriate DCI,extract the details of the PUSCH resource allocation, and transmituplink data, at first comprising a buffer status report, and/or latercomprising a portion of the buffered data, in the allocated resources.

Although similar in structure to downlink subframes, uplink subframeshave a different control structure to downlink subframes, in particularthe upper 309 and lower 310 subcarrier/frequencies/resource blocks of anuplink subframe are reserved for control signalling rather than theinitial symbols of a downlink subframe. Furthermore, although theresource allocation procedure for the downlink and uplink are relativelysimilar, the actual structure of the resources that may be allocated mayvary due to the different characteristics of the OFDM and SC-FDMinterfaces that are used in the downlink and uplink respectively. InOFDM each subcarrier is individually modulated and therefore it is notnecessary that frequency/subcarrier allocation are contiguous however,in SC-FDM subcarriers are modulation in combination and therefore ifefficient use of the available resources are to be made contiguousfrequency allocations for each UE are preferable.

As a result of the above described wireless interface structure andoperation, one or more UEs may communicate data to one another via acoordinating eNodeB, thus forming a conventional cellulartelecommunications system. Although cellular communications system suchas those based on the previously released LTE standards have beencommercially successful, a number of disadvantages are associated withsuch centralised systems. For example, if two UEs which are in closeproximity wish to communicate with each other, uplink and downlinkresources sufficient to convey the data are required. Consequently, twoportions of the system's resources are being used to convey a singleportion of data. A second disadvantage is that an eNodeB is required ifUEs, even when in close proximity, wish to communicate with one another.These limitations may be problematic when the system is experiencinghigh load or eNodeB coverage is not available, for instance in remoteareas or when eNodeBs are not functioning correctly. Overcoming theselimitations may increase both the capacity and efficiency of LTEnetworks but also lead to the creations of new revenue possibilities forLTE network operators.

Device-to-Device Communications

D2D communications offer the possibility to address the aforementionedproblems of network capacity and the requirement of network coverage forcommunications between LTE devices. For example, if user data can becommunicated directly between UEs only one set of resources is requiredto communicate the data rather than both uplink and downlink resources.Furthermore, if UEs are capable of communicating directly, UEs withinrange of each other may communicate even when outside of a coverage areaprovided an eNodeB. As a result of these potential benefits, theintroduction of D2D capabilities into LTE systems has been proposed.

FIG. 4 provides a schematic diagram of a mobile communications system400 that is substantially similar to that described with reference toFIG. 1 but where the UEs 401 402 403 are also operable to perform directdevice-to-device D2D) communications with one another. D2Dcommunications comprise UEs directly communicating data between oneanother without user and or control data being communicated via adedicated coordinating entity such as an eNodeB. For example in FIG. 4communications between the UEs 401 402 403 415 and the eNodeB 404 are inaccordance with the existing LTE standard, but as well as communicatingvia the uplink and downlinks 405 to 410, when the UEs 401 to 403 arewithin range of each other they may also communicate directly with oneanother via the D2D communication links 411 to 414. In FIG. 4 D2Dcommunications links are indicated by dashed lines and are shown toexist between 401 and 402, and 402 and 403 but not between 401 and 403because these UEs are not sufficiently close together to directlytransmit and receive signals to and from one another. D2D communicationslinks are also shown not to exist between 415 and other UEs because UE415 is not capable of D2D communications. A situation such as thatillustrated in FIG. 4 may exist in an LTE network where UE 415 is adevice not compliant with the specifications for D2D operation. It haspreviously been proposed to provide some arrangement for device todevice communication within standards which define communicationssystems according to specifications administered by the 3GPP referred toas Long Term Evolution (LTE). A number of possible approaches to theimplementation of LTE D2D communications exist. For example, thewireless access interface provided for communications between UEs andeNodeB may be used for D2D communications, where an eNodeB allocates therequired resources and control signalling is communicated via the eNodeBbut user data is transmitted directly between UEs.

The wireless access interface utilised for D2D communications may beprovided in accordance with any of a number of techniques, such ascarrier sense multiple access (CSMA), OFDM or a combination thereof forexample as well as an OFDM/SC-FDMA 3GPP LTE based wireless accessinterface. For example it has been proposed M document R2-133840 [1] touse a Carrier Sensed Multiple Access, CSMA, co-ordinations oftransmission by UEs, which is un-coordinated/contention based schedulingby each UE. Each UE first listens then transmits on an unused resource.

In another example, UEs may communicate with each other by negotiatingaccess to a wireless access interface directly, thus overcoming the needfor a coordinating eNodeB. Examples of previously proposed arrangementsinclude those in which one of the UEs of the group acts as a controllingentity to co-ordinate the transmissions of the other members of thegroup. Examples of such proposals are provided in the followingdocuments:

-   -   [2] R2-133990, Network control for Public Safety D2D        Communications; Orange, Huawei, HiSilicon, Telecom Italia    -   [3] R2-134246, The Synchronizing Central Node for Out of        Coverage D2D Communication; General Dynamics Broadband UK    -   [4] R2-134426, Medium Access for D2D communication; LG        Electronics Inc

In another arrangement one of the UEs of the group first sends ascheduling assignment, and then transmits data without a centralscheduling UE or controlling entity controlling the transmissions. Thefollowing documents provide examples of this de-centralised arrangement:

-   -   [5] R2-134238, D2D Scheduling Procedure; Ericsson;    -   [6] R2-134248, Possible mechanisms for resource selection in        connectionless D2D voice communication; General Dynamics        Broadband UK;    -   [7] R2-134431, Simulation results for D2D voice services using        connectionless approach; General Dynamics Broadband UK.

In particular, the last two contributions listed above, R2-134248 [6],R2-134431 [7], discuss the use of a scheduling channel, used by UEs toindicate their intention to schedule data along with the resources thatwill be used. The other document R2-134238 [5], does not use ascheduling channel as such, but deploys at least some predefinedresources to send the scheduling assignments.

Other example arrangements discussed in [8] and [9] require a basestation to provide feedback to the communications devices to controltheir transmissions. Document [10] discusses an arrangement in which adedicated resource exchanging channel is provided between cellular userequipment and device-to-device user equipment for interference controland resource coordination.

As a result of the possible approaches to the organisation of a D2Ddevices and networks, a number of scenarios may arise. A selection ofexample scenarios is provided by FIGS. 5a to 5d . In FIG. 5a UEs 501 and502 are outside of a coverage area of an eNodeB. Such a scenario mayoccur in public safety communications for example, where either the UEsare outside of a coverage area or where the relevant mobilecommunications network is not currently functioning correctly. In FIG.5b UE 501 is within a coverage area 504 of an eNodeB 503 and isperforming D2D communications with UE 502 which is outside the coveragearea 503. In FIG. 5c both UE 501 and 502 are within the coverage area ofthe eNodeB 503. In FIG. 5d a fourth more complex D2D scenario isillustrated, where UE 501 and UE 502 are each within the coverage areas504 505 of different eNodeBs 503 and 504 respectively. FIG. 5a to 5dillustrates just four of a large number of possible D2D usage scenarios,where further scenarios may be formed from combinations of thoseillustrated in FIGS. 5a to 5d . For example two UEs communicating asshown in FIG. 5a may move into the usage scenario of FIG. 5d such thatthere are two groups of UEs performing D2D communications in thecoverage areas of two eNodeBs.

Co-pending EP patent application EP 14153512.0 discusses an arrangementin which communications devices which are configured to perform D2Dcommunications, the contents of which are incorporated herein byreference. The communications devices are arranged to reserve sharedcommunications resources, such as those of the PUSCH of an LTE Up-link,by transmitting a scheduling assignment messages in a predeterminedsection of resources, referred to as a scheduling assignment region,allocated for performing contentions access. As discusses inEP14153530.2, the contents of which are incorporated herein byreference, a contention resolution procedure is adopted by thecommunications devices so that if one or more communications devicestransmit scheduling assignment messages contemporaneously in the samesection of the scheduling assignment region then the communicationsdevices can detect the contentious access and re-try at a differenttime.

FIG. 6 illustrate a simplified structure of a UE for use in accordancewith the teachings of the present disclosure. The UE 600 include anantenna 604 for sending and receiving wireless signals, a tramline,(“TX”) 606 for sending signals via the antenna 604 and a receiver (“RX”)608 for receiving signals via the antenna. In other words, the UE 600 isconfigured to communicate via a wireless interface. The controller 610can control messages sent and received, for example by generatingmessages to be sent or by decoding received messages. The UE 600illustrated in FIG. 6 is representative of a typical UE in an LTEenvironment. However other UEs may be suitable for use with the presentinvention. For example, the same or similar UEs can sometimes berepresented with a transceiver in place of the TX and RX pair. Such UEsare also considered as suitable for use in accordance with the teachingsof the present disclosure.

Resources Allocation

Conventionally, UEs operating in a D2D mode will share a frequency bandand will use the resources in that band in an opportunistic manner. D2DUEs may also operate in a mode where resources are controlled by theeNodeB, however the main use case in D2D is one where the UEs try to usethe shared resources opportunistically. However, due to the nature of ashared resources environment, the risk of collisions between messagessent by different UEs is high when the UEs use resources in anopportunistic manner. In the situation where the eNodeB may not be ableto allocate resources for D2D communications, the conventional D2Dsystems can therefore be unsuitable for high reliability communications.

Additionally, D2D has been designed for use by public safety systemswhere a UE is expected to communicate messages to several UEs in thesame group. In other words, a D2D UE is expected to send mostlybroadcast messages (which can mean sometimes denoted as 1:M messages)and the D2D communications protocols have been designed with this mainuse case in mind. Even though unicast messages may be sent in such a D2Dsystem originally designed for 1:M messaging (for example by havingM=1), this system can be poorly adapted to 1:1 messaging. For example,the addressing system is limited by the number of possible addresses(e.g. 256 group IDs in LTE D2D). Also, the call flows and signalling for1:M communications and for 1:1 communications can sometimes be verydifferent. For example, 1:M communications can be more likely to beassociated with a best effort mode while 1:1 communications can be morelikely to require a higher reliability, lower latency, a higherprioritisation and/or a higher QoS. As a result, sharing resources on afrequency band or channel designed to be used for, and used for, 1:Mcommunications can be detrimental to 1:1 communications and inparticular to the resulting quality of service for 1:1 communications.

It would thus be desirable to have an arrangement where 1:1 D2Dcommunications would be facilitated. It would also be desirable to havean arrangement high reliability 1:1 D2D communications would befacilitated.

Resources Allocation—Shared Pool

In accordance with the present disclosure, there is provided anarrangement where shared D2D resources for 1:M communications areseparated from resources for 1:1 communications. The resources, or groupof resources, allocated to one of 1:M and 1:1 communications we bereferred to as one as a resource pool. Accordingly, the use of resourcesin the 1:1 resources pool may be adapted to be better suited to 1:1communications and/or may thereby be made more reliable by reducing therisk of collisions between D2D signals, in particular between D2D 1:1and 1:M communication signals. This advantageous arrangement will now bediscussed using the illustrations of FIGS. 7A to 7C as examples ofpossible implementations and embodiments.

FIG. 7A provides a first illustration of an example of resources poolallocation in accordance with the present disclosure. In this example,allocations within a frequency band f1-f2 during a time period t1-t2 isbeing considered. The resources 700 available for this frequency bandand for this time period are divided between two resources pool. Thefirst resources pool 710 is allocated to 1:1 D2D communications whilethe second resources pool 720 is allocated to 1:M D2D communications.Although in this example only one frequency sub-band is allocated to the1:1 resources pool and one frequency sub band is allocated to the 1:Mresources pool, in other examples, a plurality of frequency sub-bandsmay be allocated to one or both of the 1:1 and 1:M resources pools.

Accordingly D2D communications on a shared frequency band may beallocated resources based on whether the communications are broadcast orunicast communications. In some examples, when no unicast communicationsare expected to take place on the shared band, all of the resources 700may be allocated to the 1:M resources pool 720 and no resources, may beallocated to the 1:1 resources pool 710. In this case, conventional 1:MD2D communications can advantageously use all of the resources 700 andthus use more resources than available in resources pool 720 in theexample illustrated in FIG. 7A. Also, if necessary, variations could bemade to the communications protocols and/or methods of communicating onthe 1:1 resources pool which may make the use of the resources pool moreadapted to unicast communications.

In the example of FIG. 7A the resources have been divided between 1:Mand 1:1 communications resources pools on a frequency only basis but inother examples the resources may be allocated to the two resources poolsbased on alternative and/or additional criteria.

For example, FIG. 7B provides a second illustration of an example ofresources pool allocation in accordance with the present disclosure. Inthe example of FIG. 7B, the resources are being divided between 1:M and1:1 communications resources pool on a time only basis. During the timeperiod t1-t2, the resources 700 are being allocated across the band to1:M communications during three separate time sub periods 721, 722 and723. On the other hand, doing the same time period, the resources 700are being allocated across the band as well to 1:1 communications duringtwo separate time sub-periods 711 and 712. As for the example of FIG.7A, separate resources pools are dedicated to unicast and to multicastcommunications thereby reducing the risk of collisions between the twotypes of communications and enabling the tailoring of communications tounicast, or magic as communications, if needed.

The examples of FIGS. 7A and 7B illustrates two simple ways ofallocating resources to the 1:1 and 1:M resources pools. However, anyother suitable ways of allocating resources may be used at point in timeand may be changed at a different point in time if appropriate. Forexample, FIG. 7C provides a third illustration of an example ofresources pool allocation in accordance with the present disclosure. Inthis example, a frequency band is considered during a time period t1-t3.As a point in time t2 between t1 and t3, the respective resourcesallocations for the 1:1 and 1:M communications pools are changed. Insome examples, such a change may occur on a periodical basis (farexample every subframe frame, n subframes and/or n frames with n≥2), onan event-triggered basis, on a user request basis, on a network requestbasis, on any other suitable basis and/or on any combination thereof. Inthe illustration of FIG. 7C, between t1 and t2, the resources pools areallocated resources on a time and frequency basis with blocks 711 and712 allocated to 1:1 resources pool and the remainder of the resourcesfor that period allocated to 1:M resources pool. On the other hand,between 12 and t3, the resources pools allocated resources on afrequency-only basis. A first frequency band 715 within f1 and f2 isallocated to the 1:1 resources pool while two separate frequency bands725 and 726 are allocated to the 1:M resources pool.

Depending on an expected or anticipated level of 1:1 communications, therelative sizes of the 1:1 resources pool and 1:M resources pool may beadjusted to better suit the anticipated need for resources for unicastand multicast D2D communications. For example, all of the resourcesavailable for D2D communications may be allocated to 1:M communicationsby default and in the event that 1:1 communications are expected,additional resources may be allocated for D2D 1:1 communications and/orresources previously allocated to the 1:M resources pool may now beallocated to the 1:1 resources pool. The decision to change the size orsizes of any of the resources pools may be made by any suitable elementof the mobile communication system, such as a UE or an eNodeB. Thecommunication of the resources distribution between 1:M and 1:1resources pools is further discussed below at least in respect of FIGS.15 to 17. In some examples, UEs may be required to communicate anadvance warning that they intend to use 1:1 communications and theseadvance warning messages may be used for the purpose of sizing one ormore resources pools (or allocating resources from a resource pool to1:1 communications). This may involve a UE sending broadcast messageusing 1:M resources for sending a warning and then using 1:1 resourcesfor its 1:1 communications.

As mentioned above, the resources pools may have any appropriatedistribution within the available resources and this distribution maychange with time. In the remainder of the present disclosure, theresources pool will be illustrated in simplified manner as illustratedfor example in FIG. 8, which provides examples of an example ofresources pool illustrations in accordance with the present disclosure.The three illustrations of FIG. 8 are logical illustrations andrepresents three different possible views of one and the same 1:1 and1:M resources pools allocation or distribution. The 1:1 resources poolis denoted as 810, the 1:M resources pool as 820 and the overall (1:1and 1:M) D2D resources pool is denoted as 800. In the first view, theD2D pool 800 is illustrated as a single pool, without differentiating1:1 from 1:M resources. This is not necessarily indicative of thepresence of—or of the absence of—separate pools for 1:1 and 1:M D2Dcommunications. In the second view, where separate 1:1 and 1:M pools areprovided, the pools are illustrated as adjacent groups of resources.Again, this illustration is only logical and the corresponding resourcesmay in fact be physically non-adjacent (e.g., in time and/orfrequency)—or may be adjacent. Likewise, in the third view, theresources pools are represented as non-adjacent pools, however thecorresponding resources may be physically adjacent (e.g. in time, and/orfrequency)—or may not be adjacent. Also, even though the pools arerepresented as single blocks, they may in fact be formed of one or moreblocks of resources. As the skilled person will thus understand, theseviews are logical views which do not intend to accurately represent thephysical distribution of the resources of each pool. For example, thethree views of FIG. 8 may provide an accurate logical representation ofa single example of D2D resources allocation. In other words, suchrepresentations do not imply that the actual physical time and frequencyresources are allocated to the pools in a way that maps onto therepresentations of FIG. 8. The same principle applies to theillustrations of FIGS. 9 and 11-14.

By separating D2D resources for 1:1 communications from resources for1:M communications, the risk of collisions between signals from the twodifferent types of communications can thereby be reduced. As a result,the quality of service for 1:1 communication's (which are more likely tobe high reliability communications) can be improved. However, becausethe 1:1 resources pool is shared between all 1:1 D2D UEs there is stilla risk of collisions between D2D signals sent using the 1:1 resourcespool.

FIG. 9 provides an example of grouping within a resources pool inaccordance with the present invention. This figure illustrates anexample where resources from the 1:1 resources pool can be furtherallocated to one or more sub-grows with a view to improving the qualityof service and/or to reducing the risk of collisions for 1:1communications. In the specific example of FIG. 9, the 1:1 resourcespool is divided into sub-groups: group A and group B. In this example,the preferred or most appropriate group for one UE is selected based onthe expected type of transmissions from that UE. Group A is for UEshaving frequent transmissions while group B is for UEs having lessfrequent transmissions. For example UEs in group A may be sendingfrequent but small messages while UEs in group B may be sending biggermessages but less frequently. Conventionally, these UEs would all besharing the D2D resources. In accordance with the present disclosure, byseparating these UEs from 1:M UEs, the level of service available to 1:1D2D UEs can be improved and optionally, by separating 1:1 UEs dependingon the size, number and/or frequency of expected communications forthese UEs, this level of service can further be improved as discussedbelow.

In the example of FIG. 9, UEs A1 and A2 send frequent but smallmessages. In one example, such frequent but small messages can bekeep-alive messages from idle UEs or periodical small update messages. Adevice may far example be expected to send a very brief message (e.g.“0”) every minute to confirm that the device is still active and isfunctioning correctly. Such messages would not be critical and if one ormore messages are lost due to collisions or interferences, a correctiveaction or monitoring alert would not necessarily occur. Still in theexample of FIG. 9, UEs B1-B5 send fewer but bigger messages. Forexample, these messages can be longer messages (e.g. text and/ormultimedia reports, images) but which are send less frequently and whichrequire a higher reliability. In situation where UES A1-A2 and B1-B5where to share the same resources, the frequent but small messages fromUEs A1 and A2 would like cause collisions with the traffic coming fromUEs B1-B5. Also, due to the size of the messages to be sent by B1-B5,resending these messages would use a large amount of resources and wouldthus not be resource-efficient. On the other hand, by separating UEsA1-A2 from UEs B1-B5, the small but frequent messages would not collidewith the messages from B1-B5 and therefore the communications from B1-B5are more likely to be successful first time. In turn, the amount ofresources needed for B1-B5 to send their messages would be reduced.

It is noteworthy that even though the expected level of reliability hasbeen discussed above in respect of FIG. 9, it may not always be takeninto account when deciding whether you really should be communicatingwith one group or another. For example, as mentioned above, byseparating frequent transmissions from other transmissions the risk ofcollisions associated with the frequent transmissions can be reduced,regardless of the frequent or non-frequent transmissions requiring aspecific level of reliability, if any.

Additionally in the example of FIG. 9 the 1:1 resources pool has beendivided into two groups. However in other examples, the 1:1 resourcespool may be divided into three or more groups based on any suitablecriteria. For example it could be divided into a first group “group A”for frequent high reliability transmissions, a second gnaw “group B” forfrequent but low reliability transmissions and a third group “group C”for less frequent transmissions (e.g. regardless of any reliabilitylevel). Other criteria include for example a preferred or required QoSlevel, a preferred or required latency.

Preferably, in an arrangement where UEs are divided based on thefrequency amount of traffic expected from them, a group should havefewer UEs if it is for frequent transmissions then a group for lessfrequent transmissions. For example, if too many UEs are associated withgroup A of FIG. 9, the collisions between the transmissions from the UEscould be such that the quality of service within that group would bedrastically reduced. Likewise, it would be desirable for group B toinclude as many UEs as possible while preserving a certain level ofservice of quality of service. In some examples, the total size of theresources for each group or the related size of the resources for eachgroup may be fixed or maybe changed when appropriate.

Also, if it is believed that a group comprises two many UEs for it tofunction in an optimal manner, this group may be subdivided into twogroups if such a subdivision improves the quality of service and/ormakes system more efficient. For example, it may be found at in somesituations having a large amount of resources for or a group Bcomprising a large number of UEs is less efficient than having twogroups having a small amount of resources and a smaller number of UEs.In this situation, the decision on which groups should be used for whichcommunications is also based a number of UEs within one or more of thegroups. In other examples, this decision may additionally oralternatively be based on one or more further criteria, such as expectedlevel of collision between communications from a group's UEs. In theexample of FIG. 9, if the UEs in group A require a higher reliabilitythan the UEs in group B, the UEs may be associated with one of group Aor group B so that an expected level of collisions within group A islower than the expected level of collisions within group B.

The decision on how to allocate resources to the groups within the 1:1resources pool and/or on how to decide which group should be associatedwith a UE may be made by any suitable element. In one arrangement anetwork element, e.g. a eNodeB be, decides which resources are allocatedto each group and decide on the criteria for identifying the mostsuitable group and communicate this information to the UEs. A UE maythen decide to which group it should be associated based on the criteriareceived from the eNodeB and based on its own expected level ofcommunication (e.g. frequency, size of messages, reliability, etc.). AUE may know the traffic load in the group/resource pool by performinginterference measurements such as Resource Signal Receive Power (RSSI),Reference Signal Received Power (RSRP), and Reference Signal ReceivedQuality (RSRQ). A UE may measure its own traffic activity/inactivityusing, for example, the inactivity timer and/or buffer status. Inanother example arrangement, the UEs may already have stored apredetermined set of criteria for selecting a group and the UEs may beable to derive which of the 1:1 pool's resources are allocated to agroup to be used from for example an identifier for that group.

Therefore, in accordance with the present disclosure, there is providedan arrangement where resources within the 1:1 resources pool can beallocated for use by one or more groups and/or sub-groups of 1:1 D2DUEs. The resources allocated to one of these groups and/or sub-groupsmay be referred to as a sub-pool as it provides a pool of resourceswithin the 1:1 resources pool. It is also noted that a 1:1 resourcespool divided into n separate groups may also be viewed or treated as nseparate 1:1 resources pools. In other words, it is within the scope ofthe present disclosure that the plurality of 1:1 resources pools may beprovided and the principles and teachings discussed herein in respect ofgroups within a single resources pond apply equally to a privately ofresources pools.

Advantageously, and even though resources within a pool or sub-pool maybe shared between two or more corresponding D2D UEs, by dividing the 1:1UEs into two or more groups, some of the disadvantages and of thenegative effects of resources sharing can thereby be reduced.

Resources Allocation—Dedicated Resources Pool

In the examples illustrated above, the reliability level provided to D2Dterminals can be improved if required. However, because several UEs maybe sharing resources within a pool and/or group, the risk of collisionsmay in some cases still be too high for the type of communications to beused. Some communications may require a very high level of reliabilitywhich may not be well suited for, or compatible with the sharing ofresources between UEs.

FIG. 10 provides an example use case for 1:1 D2D communications in avehicle convoy environment. In this example, each of the vehicles A-D isprovided with a mobile communications unit which is configured tocommunicate using at least D2D communications. For example the mobilecommunications unit may be a LTE unit which can be used in aconventional mode (communicating with a eNodeB) and in a D2D mode(communicating with other D2D devices). In this convoy the first vehiclecontroller A is the head of the convoy and communicates with at leastthe next vehicle follower B. In terms, follower B communicates with thenext vehicle follower C which itself communicates with the next vehiclefollower D. In this case, it is critical that the communications betweenA and B, B and C, and C and D do not suffer from a high level ofcollisions or a low quality of service. While some aspects of how toimprove the overall quality of service may not be considered under thepresent disclosure, by reducing the level of collision forcommunications between the vehicles, the quality of service may besignificantly improved which in turn contributes to the safety of thevehicles A-D. In the event that too many collisions occur, a messagefrom one vehicle to a neighbouring vehicle may require severalretransmissions which would delay the communications and may havedisastrous consequences for the convoy. Accordingly, within a resourcespool (or as a resources pool), there may be provided resources which areallocated to one UE only (e.g. for all communications from/to this UE orfor all communications between this UE and another UE). Such resourcesmay be allocated for one of, or any combination of, a first UE'stransmitter a first UE's receiver, a second UE'S transmitter and asecond UE's receiver. Cases where resources are allocated to one UE,transmitter or receiver only will sometimes be referred to as cases ofdedicated resources allocation in the present disclosure.

FIG. 11 provides an illustration of an example of dedicated resourcesallocations based on sources in accordance with the present disclosure,where resources have been allocated to the transmitter of the three UEsA-C. This has been represented in FIG. 11 by the three boxes 1111, 1112and 1113 within the 1:1 resources pool 1110. In this example, resources1111 are reserved or dedicated for UE A to transmit signals whileresources 1112 and 1113 are reserved or dedicated for UE B and C,respectively, to transmit signals. Accordingly signals transmitted byUEs A-C should not interfere with each other, i.e. should not collide,and should not interfere with any other signals from any other UE—forexample UE D. As a result, the risk of collisions between the D2D UEssharing the resources can be reduced and the level of reliability forUEs A-C can be improved. However as a result of the reserving ordedicating of the resources to individual UEs, their receiver and/ortheir transmitters, the resources may not be used as efficiently aspreviously because the dedicated resources should not be used by anyother UEs even at times when the specific UE to which they are allocatedis not using it dedicated resources to transmit signals. This is atrade-off to be taken into account when deciding how best to use theresources in the 1:1 resources pool(s): using dedicated resources canimprove reliability while reducing the overall throughput and on theother hand, when two or more UEs share resources, the throughput may beincreased but the risk of collisions would also increase (which canreduce reliability).

It is noteworthy that the examples (above or below) where resources arededicated to one UE (or its receiver or transmitter) can be viewed as apassible use of the previously discussed groups. The “grouping”—aspreviously discussed—is in this case based on one of a UE, a UE'stransmitter and a UE's receiver, with only a single one of them in thegroup and optionally paired with another UE (its receiver and/ortransmitter). In other words, it can be viewed as a “grouping” asdiscussed above even though each group is limited to one element, wherean element is a UE a UE's transmitter, a UE's receiver, or any of thesepaired with another UE, another UE's transmitter or another UE'Sreceiver. As a result, the teachings discussed in respect of the groupsor resources pools above apply equally to any system, method orapparatus using dedicated resources.

FIG. 12 provides another illustration of an example of dedicatedresources allocations based on destinations in accordance with thepresent disclosure. In this second example of dedicated resourcesallocations, the resources in the 1:1 resources pool 1210 are allocatedto a single receiver. In FIG. 12, three of the four UEs A-D haveresources allocated far their receiver. UE A, UE B and UE C haveresources 1211, 1212 and 1213, respectively, allocated from the 1:1resources pool to their receivers. The resources 1211 can thus only beused for signals to be sent to the UE A. In some examples, theseresources may thus be shared by a plurality of UEs which may communicatemessages to UE A. In some examples, even though the resources maytheoretically be used by a plurality of UEs, in practice they may onlybe used by one UE. For example, in the use case illustrated in FIG. 10,it is unlikely that a UE other than follower B would transmit messagesintended for the receiver of controller A and therefore resourcesallocated to the receiver of UE A would not in practice be shared by twoor more UEs. In other words in this case it may be sufficient toallocate resources for the receiver of UE A regardless of the UEtransmitting signals to achieve the expected result.

In the present disclosure, when allocating resources to a single UE isdiscussed, this wording is intended to mean allocating resources forcommunications to and from the UE. Resources allocated to a single UEmay thus be used for D2D 1:1 communications from this UE to any otherD2D UE and for D2D 1:1 communications for this UE and from any other D2DUE. Likewise, resources can be allocated—or dedicated—to a singletransmitter (for D2D 1:1 communications from this UE to any other D2DUE) or to a single receiver (for D2D 1:1 communications for this ITE andfrom any other D2D UE)

FIGS. 13A-13B provide an illustration of an example of dedicatedresources allocations based on sources and destinations in accordancewith the present disclosure. In the example of FIG. 13A, the 1:1resources pool 1310 includes three sub-pools 1311, 1312 and 1313 forresources allocated to communications between UE A-UE B; UE A-UE C; andUE B-UE C, respectively. Within each sub pool, resources are allocatedto further sub-pools and separately for communications from a first UEto the other UE and for communications from the other UE to the firstUE. For example, resources 1311-1 are allocated for communications fromA to B, resources 1311-2 are allocated for communications from B to A,resources 1312-1 are allocated for communications from A to C, resources1312-2 are allocated for communication from C to A, resources 1313-1 areallocated to communications from B to C and resources 1313-2 areallocated to communications from C to B. In the previous sentence theterm “allocated” can be read as “dedicated” within the meaning of thepresent disclosure as the resources are allocated exclusively to a pairof a UEs transmitter and another UE's receiver.

In the example of FIG. 13B, the resources 1310 of the 1:1 resources poolare allocated to three sub-pools 1311, 1313 and 1314 for the four UEsA-D. More specifically, resources within sub-pool 1311 are divided andallocated to communications from A to B (1311-1) and from B to A(1311-2), resources within sub-pool 1313 are divided and allocated tocommunications from B to C (1313-1) and C to B (1313-2) and resourceswithin sub-pool 1314 are divided and allocated to communications from Cto D (1314-1) and D to C (1314-2). The example of FIG. 13B may forexample be suitable for use in the example situation of FIG. 10. In thisexample also illustrates that the dedicated resources may not beallocated to all possible combinations of UEs, UEs' receivers and/ortransmitters. For example, the 1:1 resources pool 1310 of FIG. 13B doesnot include any resources allocated specifically for communicationsbetween UE A and UE C or D. In some cases, UE A may still communicatewith UE C for example using shared resources (or non-dedicatedresources) of the resources pool 1310. In other cases UE A may not beable to communicate with UE C for example because there are no remainingresources available for these communications, because UE A and UE C aretoo far apart to communicate with each other, etc.

In the arrangements of FIG. 13A-13B, the use of resources is likely tobe less efficient than in an arrangement where the UEs share all of theresources of 1311, 1312, 1313 and/or 1314 in the single sub-pool, and insome cases significantly less efficient. However, in the event that anyof the UEs wishes to send messages to another of the UEs, it should notexperience any collisions from messages from the other UEs. In otherwords, the level of reliability that can be offered can thereby beimproved. Therefore, depending on the requirements and possibly on acase-by-case basis, the resources may be allocated in a shared ordedicated manner so as to suit the situation as well as possible. Ofcourse, the UEs could still experience collisions and/or interferenceswith messages or signals sent by other devices using the same resources,for example from devices using LTE (e.g. from another mobile network),WiFi, Bluetooth of any other technologies. This is likely to be out ofthe control of the MNO, however by using dedicated resources the MNO canreduce collisions and interferences between messages from its UEs andthus improve the reliability of the message delivery in the 1:1 D2Dprotocol.

FIG. 14 provides an illustration of an example of dedicated resourcesallocations based on a source-destination pair. In this example the 1:1resources pool 1410 comprises three sub-pools 1411, 1412 and 1413. Thefirst sub-pool 1411 is dedicated to communications between UEs A and Bwhile the second and third sub-pools (1412 and 1413, respectively) arededicated to communications between UEs A and C and UEs B and C,respectively. This example of resources allocations is somewhat similarto the example of FIG. 13A but where resources are not allocatedspecifically in one direction of communication between a pair of UEs.This arrangement may be sufficient to provide an acceptable level ofreliability as each UE may be able to recover messages sent by the otherUE and which collided with its own messages as it is aware of thedetails of its own messages which caused the collision. In otherexamples, even if no such recovery is attempted, depending on the typeof communications between UEs A and B the risk of collisions betweenmessages between the two UEs may not be significant enough to warrant anarrangement as illustrated in FIG. 13A. For example if mostcommunications originate from UE A and the communications from UE B to aUE A consist mostly of acknowledgement messages, the amendmentillustrated in FIG. 14 may be fully satisfactory. This situation canpresent itself if for example UE A is a home equipment device and UE Bis a home devices monitoring centre. The home equipment device may sendregular reporting messages (for example every hour) to the centre whichacknowledges successful receipts of the reporting messages. The centremay communicate mostly with the remote server to send reports based ondevices' reporting messages received on a regular basis (for exampleevery day).

As will be understood by the skilled person, the various andillustrative examples discussed above may be adapted and/or combined inany suitable manner. For example, resources far some of the UEs may beshared, while other UEs have resources allocated specifically for theirtransmitter, while other UEs have resources allocated specifically fortheir receiver and another UE's transmitter, etc.

According to the present disclosure, there can therefore be provided anarrangement where the allocation of D2D resources can be improved so asto better suit the needs of 1:1 communications. As a result, devicesusing 1:1 communications may be segregated from devices using 1:Mcommunications such that 1:M communications should not close collisionsor interferences with 1:1 communications. Additionally (and optionally),the 1:1 resources may be further divided depending on the type of 1:1communications (e.g. frequency of transmission reliability preferencesor requirements, latency preferences or requirements, device ID, serviceor type of service associated with the 1:1 communications, etc.).Therefore, a system which is originally designed for 1:M communicationsand not for 1:1 communications, can be improved so as to betteraccommodate 1:1 communications while limiting the impact on theconventional, existing and/or legacy (1:M) D2D communications system.

Depending on the situation, the extent to which the 1:1 resources areshared or not can be varied. For example, on one hand, the 1:1 resourcespool may be shared amongst all D2D devices sending 1:1 communications.On the other hand, in other examples, the 1:1 resources may all bededicated to a UE, a UE's receiver or a UEs transmitter (possibly panedwith one of another UE, another UE's receiver or another UE'stransmitter) and may thus not be shared between UEs. Of course, in someexamples, the 1:1 resources may be allocated wing an intermediate schemeor way of a resources allocation based on a combination of shared anddedicated resources.

In some cases the use of shared resources allocation may be preeminent.For example it may be useful in cases with relatively infrequenttransmissions such as one-off transmissions of a large volume of data.In these cases, if a high level of data loss is not acceptable, aconventional arrangement using resources shared with 1:M communicationsmay not be appropriate due to the risk of collisions but sharingresources with 1:1 communications having for example the same profilecan provide a satisfactory arrangement due to the low risk ofcollisions. From a more general point of view, using 1:1 sharedresources has the advantage of providing an arrangement where resourceutilization is more efficient (compared to dedicated resources) therebyreducing the risk of a lack of resources. It also enables a reduction inthe risk of collisions (compared to sharing resources with conventionalD2D 1:M communications). However, even though this risk of collisionshas been reduced, it is still present as the 1:1 resources are shared bydevices for use for 1:1 communications. Therefore, this 1:1 sharedresources scheme may be appropriate in cases where this lowered risk ofcollisions has been lowered enough to reach an acceptable level butthere may be cases where this lowered risk may still remain too high tobe satisfactory. As the skilled person will understand collisions canaffect the quality of the communications in the number of ways, such asby increasing latency, by decreasing throughput, by preventingsuccessful communications altogether.

In other cases, the use of dedicated resources allocation may bepreeminent. For example it may be useful in cases where only a very lowlevel of data loss is acceptable and where the risk of lacking resourcesmay be relatively low. In these cases, even the improved (i.e. reduced)number of collisions provided by shared 1:1 resources discussed abovemay not be sufficient to attain a suitably low level of collisions. Froma more general point of view, using 1:1 dedicated resources has theadvantage of providing an amendment where resources are guaranteed andcollisions with other D2D transmissions can be avoided altogether. As aresult, transmissions delay and a number of errors can thereby bereduced and the quality of service provided can therefore be improved.On the other hand, dedicated resources allocation can provide anarrangement where resources utilisation is less efficient compared toshared 1:1 resources. This is because the resources are dedicated, i.e.allocated or reserved, to the relevant element(s) regardless of theelement(s) actually transmitting signals are not. Also, depending on thenumber of elements to which resources are to be dedicated, the amount ofresources dedicated for each element or pair of elements may be low.This is because the 1:1 resources to be allocated in a dedicated modewill have to be divided between the elements (or pairs of elements) andthus if many elements will have resources dedicated to them, they arelikely to have a small amount of resources dedicated to them. As aresult, the throughput available to each element may be very low. It maytherefore not be suitable to use dedicated 1:1 resources for situationswhere there are a large number of UEs using 1:1 communications and/orwhere a large volume of data is to be transmitted. In this context, theterm “element” refers to a UE, a UE's receiver or a UE's transmitter.

Therefore, it can be decided how best to allocate the resources in the1:1 resources pool taking into account a number of elements such as:specific requirements, the type of D2D UEs, the type of communicationsto be sent using the D2D protocols, latency requirements, collisionrequirements, throughput requirements, etc. it is noteworthy that in thepresent sentence, the term “requirements” can also be read andinterpreted as “preferences”.

Resources Allocation—Allocating and/or Releasing Resources

The decision on how to best allocate resources using shared and ordedicated allocation schemes may be made by any appropriate unit forexample an eNodeB of a UE. Also the unit responsible for deciding how toallocate the 1:1 resources of the resources pool may depend on thesituation at hand. For example, in D2D in-coverage situations, an eNodeBmay be considered as being an appropriate unit for making this decisionwhile in a D2D without out-of-coverage situation UE may be considered asbeing appropriate unit for making decision.

As will be understood, in accordance with the present disclosure thereare two types of resources allocations:

1. High-level allocations for allocations of D2D resources to 1:M and/or1:1 resources pools and optionally, for allocations of D2D 1:1 resourceswithin the 1:1 resources pool (for example using shared and/or dedicatedresources allocation).

2. Low-level allocations for allocation of resources for actual UE'stransmissions. The resources to be used in a low-level allocation willof course depend on a high-level allocation. For example, resourcesallocated for a UE to transmit a 1:1 message would be selected from the1:1 resources pool and not from the 1:M resources pool.

High-level and low-level allocation messages may be sent using anysuitable method and may for example be sent using 1:M D2D resources. Insome situations, the 1:M resources pool may always be available to UEsby default and the availability of the 1:1 resources pool(s) for UEs, ifany, may be communicated via a broadcast message sent using the 1:Mresources pool. For example, if it is detected that an existing 1:1resources pool is becoming saturated while the 1:M resources pool isunderused, it may be decided that resources previously in the 1:Mresources pool may now be transferred to the 1:1 resources pool. The new1:1/1:M resources pools configuration may then be communicated to UEsusing a broadcasted message.

Once the 1:1 and 1:M resources pools configuration is known, resourceswithin a 1:1 resources pool may be allocated in several possible ways.

In some situations, in particular are for some in-coverage cases, theresources within the 1:1 resources pool may be allocated by the eNodeB.When the UE enters the RRC connected state, the eNodeB may then allocateresources from the 1:1 resources pool for use by this UE.

In other cases, in particular for some out-of-coverage situations, oneof the UEs may be acting as a cluster head (CH) and may allocateresources from the 1:1 resources pool. For example, when a UE enter theRRC connected state, the UE can request a one-to-one bearer connectionand in response to this request the CH UE may allocate resources fromthe 1:1 resources pool to this UE.

In yet other cases, the resources may be allocated by the transmittingUE. For example if a UE intends to send a 1:1 message, it may broadcasta resources allocation message using 1:M resources wherein the resourcesallocation message identifies resources from the 1:1 resources pool thatthe transmitting UE will be using for transmitting data.

In other examples, low-level allocation messages may not be required.For example, if as a result of the high-level allocations, a UE A hasbeen allocated dedicated resources for communicating to UE B, UE A doesnot have to send a low-level allocation message and it may instead startcommunicating to UE B straightaway using the dedicated resources.

In further examples, the resources allocation may be pre-configured.Even though this example implementation may only be practical in a morelimited number of situations, it could be beneficial to havepre-configured UEs which are aware of the high-level or low-levelresources allocations. This may be particularly useful in situationswhere the number of UEs is small. For example, the position of the 1:1resources pool may vary depending on a cell or available resources whilethe relative position of the resources to be used by a specific UE maybe maintained relative to the pointer to the 1:1 resources pool'sposition. For example, once a UE is aware of the position of the 1:1resources pool, the UE can automatically determine or derive theresources to use to communicate based on the location of the 1:1resources pool. Advantageously (and as in the previous case), allocationmessages and procedures may not be required and the system can besimplified.

In some example, the resource mapping for pre-configuration cases can beimplemented using at least a hash function and/or any other suitablefunction. The hash function may use any suitable input, such as forexample any one of or combination of

(i) an ID for the source UE (e.g. Prose ID, IMSI, etc.);

(ii) an ID for the destination UE (e.g. Prose ID, IMSI, etc.);

(iii) additional input (e.g. start position of resource pool, cellid(PCI), data size, transmit/receive type, time information, etc.)

The output of the hash function may help determine a resource indexindicating unique resources. For example the resource index may indicatethe following information, or the following information may be derivedfrom the index: frequency position (resource block, resource element),time (symbol, slot, and subframe), space (antenna), code (orthogonalcode number), etc.

In examples where low-level allocation is taking place, the allocationmay be carried out in different ways. For example, they may be allocatedon demand, when a communication starts or is about to start, and theresources may be allocated for this communication only. In a firstimplementation, the on-demand allocation may be carried out in asemi-static manner. In this case, when the UE is in a RRC connectedstate, the resources are allocated to a UE until the communication iscompleted. In some cases, the communication being completed may coincidewith the RRC connection being torn down and the resources may beallocated until the RRC connection is released. In a secondimplementation, the UE may carry out a UE autonomous allocation. In thiscase, the UE selects resources for the communication and informs theother UEs (e.g. using a 1:M broadcasted message) of the resources itwill be using. Other UEs may then avoid using these resources with aview to reducing collisions. In a third implementation, the resourcesmay be allocated in a dynamic way. This case is similar to thesemi-static but the resources are not allocated for a specific sessionor communication. To try to avoid blocking resources for too long, atimer is then provided to determine for how long the resources willremain allocated to this UE. Once the time expires, the resources arereleased. In the event that the UE has completed its communications, nofurther steps are required but in the event that the UE has notcompleted its communications, it may have to have more resourcesallocated for its transmissions. As a result, one or more further(low-level) allocation messages may be exchanged.

FIGS. 15-17 provides illustrations of examples of possibleimplementations of (low-level) resources allocation. FIG. 15 provides anillustration of an example of resources allocations controlled by aterminal in accordance with the present disclosure. The illustration ofFIG. 15 corresponds to a case where the UE is responsible for thelow-level allocation of resources (i.e. the allocation of resourceswithin the 1:1 resources pool). This can correspond for example to thesecond implementation discussed above. The UE 1501 first autonomouslyallocates resources from shared resources of the 1:1 resources pool.Because at least part of 1:1 resources pool is shared between these fourUEs, the source UE 1501 then broadcasts (“BC”) a signal informing theother UEs 1502, 1503 and 1504 of the resources allocation. Theallocation message may for example include an ID for the UE andinformation relating to the resources position so that other UE can tryto avoid using the same resources. Then, the source UE 1501 can starttransmitting its data to the destination UE 1502 using the allocatedresources from the 1:1 resources pool.

FIG. 16 provides an illustration of an example of resources allocationscontrolled by a base station in accordance with the present disclosure.This illustration can correspond for example to the first implementationdiscussed above. In this case, a eNodeB 1601 decides which resources toallocate to the source UE 1602 for its communications to the destinationUE 1603. The eNodeB 1601 can then inform the source and destination UEsof the allocated resources. The allocation message will includeinformation relating to the position or location of the allocatedresources and may also include an ID of the source UE 1602 and possiblyof the destination UE 1603. As in this case UEs will wait for anallocation message before they start communicating and thus do notoperate in an autonomous manner as illustrated in FIG. 16, theallocation message may be sent to the source and destination UEs only.The allocation message may therefore be sent in a unicast—notbroadcast—manner. In the example of FIG. 16, the allocation message issent using RRC and/or SIB signalling, where “SIB” stands for SystemInformation Blocks. Thus, in the illustration of FIG. 16, the allocationmessage is not sent to UE 1604 which is not involved in thecommunication. Once the resources have been allocated and the allocationhas been communicated to the source and destination UEs, the source UE1602 can start transmitting data to the destination UE 1603. Once thetransmission is completed, the resources can be released. Preferably theresources will be released using signalling which mirrors the signallingfor the allocation message. As for the resources allocation messages,the resources release message may be sent to the source and destinationUEs only, not to other UEs (as illustrated in FIG. 16).

FIG. 17 provides another illustration of another example of resourcesallocations controlled by a base station in accordance with the presentdisclosure. This example is similar to the semi-static implementation asit illustrates a dynamic resources allocation (see the discussion of thethird implementation above). The first steps are similar to the firststeps of FIG. 16 with eNodeB 1701 and UEs 1702-1704 acting in a similarmanner to eNodeB 1601 and UEs 1602-1604, respectively, of FIG. 16. Oncethe allocation messages have been sent, the source UE 1702 can starttransmitting data to the destination UE 1703 via the allocated resourcesindicated in the allocation message. A timer is also set up whichdetermines when the resources allocation will expire. For example thetimer may be pre-set or may be indicated in the allocation message. Oncethe timer expires, the resources are automatically released and, byusing this timer arrangement the releasing of data can be performedwithout signalling or messaging to that effect.

In the examples of FIGS. 15-17, the resources are allocated far atransmission from a source to a destination, i.e. in one direction only.Therefore, if the destination wishes to communicate data back to thefirst UE (e.g. to send an ACK, to respond to a query, etc.) resourceshave to be allocated for the transmission in the opposite direction.This is shown for example in FIG. 18 which illustrates an example of aresources allocation and data two-way exchange. In this example UE1 1801first sends data to UE2 1802 which then sends data back to UE1. It ispointed out that the illustrations of FIG. 18-19 are simplifiedillustration and, for example, the allocation messages may not actuallybe sent by UE1 to UE2. As the skilled person will understand from theteachings of the present disclosure (see for example the discussion ofFIGS. 15-17), the allocation messages may be sent by another partyand/or may be broadcasted rather than sent specifically to UE2. Asillustrated in FIG. 18, allocation messages (identified as “SA” standingfor “Scheduling Assignment”) are sent first to indicate the resourcesres1 and res2 allocated for the first communication and the secondreturn communication respectively. Once the allocation messages havebeen received, the UEs can start transmitting data via the allocatedresources res1 and res2.

FIG. 19 provides an illustration of another example of a resourcesallocation and data two-way exchange in accordance with the presentdisclosure. This other example may be used as an alternative to thearrangement of FIG. 18. In this example, resources are allocated for atwo-way communication and therefore, a single allocation message may beused for informing the UE1 and/or UE2 of the resources allocated formessages sent to each other. The UE1 1901 can then send its data to UE2using the allocated resources res1 and, if the UE2 wishes to send anydata in return, it can do so using the same allocated resources rest.This can be particularly useful when the return communication from UE2to UE1 is relatively short because the amount of signalling to be sendmay be significant in comparison to the corresponding amount of data.For example, if the return data is merely an acknowledgement that thetransmission has been received, the overhead created by the resourcesAllocation signalling can become significant and therefore undesirable.

Resources Affixation—Possible Variations and Other Aspects

Even though 1:1 and 1:M communication have been generally presentedseparately above, it is within the teachings of the present disclosurethat one device may be configured to use both 1:1 resources and 1:Mresources. Both types of resources may be used simultaneously or not.Therefore, references to a 1:1 UE should be understood at a UE using 1:1communications (i.e. a UE which may also be using 1:M communicationbefore, simultaneously to or after 1:1 communication).

As mentioned above, dedicated resources can be viewed (1) as a sub-poolof the 1:1 resources pool or (2) as resources outside the 1:1 resourcespool wherein the pool terminology is then used only for resources whishare shared.

High reliability and high reliability communications can refer or relateto one or more of the following elements:

-   -   low error rate, error recovery, connection persistence, etc.    -   guaranteed QoS (stable, throughput/error rate ratio        requirements, etc.)    -   Low latency (minimum delay, real-time requirements, etc.)    -   High priority data

These aspects may for example be considered when deciding whether andhow resources within the 1:1 resources pool should be grouped intosub-pools (for sharing) and/or dedicated to elements (for a dedicatedresources allocation mode), or for deciding whether to use a 1:1resources pool or not altogether.

Also, depending on the amount of traffic, the traffic quality, a numberof D2D UE, etc., the resources pool may be expanded or reduced. In someexamples, the D2D system provides by default a conventional arrangement,i.e. where resources are used in a way which is particularly suited to1:M communications. If it is detected that 1:1 traffic is to be sent,some of the resources may be separated from the rest of the resourcesand reserved for 1:1 communications by creating a 1:1 resources pool. Ifit is then detected that a low level of or no 1:1 communications areexpected, the 1:1 resources pool may no longer be in use and thecorresponding resources may be return for use on the conventional way.In other words, once D2D UEs start communicating using 1:1 D2Dcommunication, a larger resource pool may be required in order to reducecollision probability, in particular with 1:M communication, and it canthus be beneficial to use a 1:1 resources pool. Likewise, depending onthe level of 1:1 traffic, the size of the 1:1 resources pool can beadjusted while maintaining the 1:1 resources pool.

Possible triggers for a resource pool's size adjustment include:

-   -   Entering RRC connected state with a request for a 1:1        communication in a case where the eNodeB controls resource pool.    -   the number of 1:1 D2D (e.g. “ProSe”) communication users at the        core network level    -   a high number of detected collision of Layer1/Scheduling        assignments

It is pointed out that, in the present disclosure, the term party mayrefer to one or more terminal device or network element.

Also the terms, user equipment (UE), communications terminal, terminal,terminal device and communications device may be used interchangeably.

Further aspects of the present disclosure are described in the followingnumbered clauses:

Clause 1. A method of allocating resources for communications in amobile telecommunication system wherein the mobile telecommunicationsystem provides a wireless interface for a base station to communicatewith communications devices and wherein a communications device isoperable to transmit signals to another communications device usingresources of the wireless interface and in accordance with adevice-to-device communication protocol,

wherein a first pool of the resources is allocated to device-to-devicecommunications of the broadcast type and a second pool of the resourcesis allocated to a device-to-device communications of the unicast type,the second pool of resources being separate from the first pool,

the method comprising:

a first communications device transmitting broadcast messages usingresources of the first resources pool; and

a second communications device transmitting unicast messages usingresources of the second resources pool.

Clause 2. A method according to any preceding clause, the method furthercomprising:

transmitting a message to one or more communications devices, themessage comprising a pool location indication wherein the position ofthe first resources pool and the position of the second resources poolcan be derived from the pool location indication.

Clause 3. A method according to any preceding clause, wherein the secondresources pool is divided into at least a first sub-pool and a secondsub-pool, wherein the sub-pools are separate from the each other, themethod comprising:

when preparing for transmitting signals using the second resources pool,the second communications device selecting one of the at least first andsecond sub-pools to use for sending the signals; and

the second communications device transmitting the signals usingresources of the selected sub-pool.

Clause 4. A method according to clause 3, wherein the method comprises:

determining that the second resources pool should be divided into atleast a first sub-pool and a second sub-pool;

upon said determination, transmitting a message to a communicationsdevice, the message comprising a sub-pool location indication whereinthe position of the first sub-pool and the position of the secondsub-pool can be derived from the sub-pool location indication.

Clause 5. A method according to clause 4, wherein the message thithercomprises an indication of one or more sub-pool selection criteria foruse by communications devices to select a sub-pool for transmittingsignals.

Clause 6. A method according to any of clauses 4 to 5, wherein saiddetermination is based on an estimated or measured level of collisionwithin the second resources pool.

Clause 7. A method according to any of clauses 4 to 6, wherein saiddetermination is based on an estimated or measured level of traffic loadwithin the second resources pool.

Clause 8. A method according to clause 7, wherein said traffic loadlevel is estimated or measured based on an interference indicator forthe second resources pool.

Clause 9. A method according to any of clauses 4 to 8, wherein saiddetermination is based on an estimated or measured level of transmissionactivity/inactivity the UE.

Clause 10. A method according to clause 9 wherein said inactivity levelis estimated or measured based on a timer for measuring non-transmissionduration in the UE.

Clause 11. A method of any of clauses 3 to 10, Wherein an indication ofone or more sub-pool selection criteria for use by the secondcommunications device to select a sub-pool for transmitting signals isstored in the second communications device.

Clause 12. A method of clause 11, wherein the one or more sub-poolselection criteria comprise one or a combination of: a reliability levelparameter, a communication type, a Quality of Service “QoS” parameter, alatency parameter, a priority parameter a throughput parameter, and amaximum number of communications devices in the sub-pool.

Clause 13. A method of any of clauses 3 to 12, the method furthercomprising:

determining that the level of collision in one of the sub-pool isunacceptable based on a comparison with a sub-pool acceptabilitythreshold;

upon determining that the level of collision in one of the sub-pool isunacceptable, re-allocating the resources of the second pool between thecorresponding sub-pools.

Clause 14. A method of any preceding clause further comprising:

determining that the level of collision in the second resources pool isunacceptable based on a comparison with a pool acceptability threshold;

upon determining that the level of collision in the second resourcespool is unacceptable, re-allocating the resources between the first andsecond pool.

Clause 15. A method of any preceding clause ether comprising:

allocating resources in the second resources pool for communications inrespect of a specific communications device.

Clause 16. A method of clause 16, wherein the resources in the secondresources pool to be allocated to communication in respect of thespecific communications device are selected based on one or acombination of: a reliability level parameter, a communication type, aQuality of Service “QoS” parameter, a latency parameter, a priorityparameter and a throughput parameter.

Clause 17. A method of any preceding clause further comprising thesecond communications device:

transmitting a first message as a broadcast message using resources ofthe first resources pool,

transmitting a second message as a unicast message using resources ofthe second resources pool, wherein the first message comprises resourcesallocation information for indicating resources of the second resourcespool used for transmitting the second message.

Clause 18. A method of any preceding clause further comprising:

allocating two-way resources for communications between the secondcommunications device and a third communications device;

the second communications, device transmitting signals to the thirdcommunications device using the allocated two-way resources; and

in response to the transmitted signals received from the secondcommunications device, the third communications device transmittingsignals to the second communications device using the allocated two-wayresources.

Clause 19. A mobile telecommunication system for device-to-devicecommunication, the mobile telecommunication system comprising a basestation; and communications devices, wherein

the mobile telecommunication system provides a wireless interface forthe base station to communicate with the communications devices;

one of the communications devices is operable to transmit signals toanother one of the communications devices using resources of thewireless interface and in accordance with a device-to-devicecommunication protocol,

wherein a first pool of the resources is allocated to device-to-devicecommunications of the broadcast type and a second pool of the resourcesis allocated to a device-to-device communications of the unicast type,the second pool of resources being separate from the first pool

a first of the communications devices is configured to transmitbroadcast messages using resources of the first resources pool; and

a second of the communications devices is configured to transmit unicastmessages using resources of the second resources pool.

Clause 20. A mobile telecommunication system according to clause 19, thesystem further comprising:

an element configured to transmit a message to one or morecommunications device, the message comprising a pool location indicationwherein the position of the first resources pool and the position of thesecond resources pool can be derived from the pool location indication

wherein, optimally the element is one of a base station and acommunications device.

Clause 21. A mobile telecommunication system according to clause 19 or20, wherein the second resources pool is divided into at least a firstsub-pool and a second sub-pool, wherein the sub-pools are separate fromthe each other,

wherein the second communications device is configured to, whenpreparing for transmitting signals using the second resources select oneof the at least first and second sub-pools to use for sending thesignals; and to transmit the signals using resources of the selectedsub-pool.

Clause 22. A mobile telecommunication system according to clause 21,wherein the system comprises:

an element configured to determine that the second resources pool shouldbe divided into at least a first sub-pool and a second sub-pool,

wherein the element is configured to, upon said determination, transmita message to a communications device, the message comprising a sub-poollocation indication wherein the position of the first sub-pool and theposition of the second sub-pool can be derived from the sub-poollocation indication,

wherein, optionally, the element is one of a base station and acommunications device.

Clause 23. A mobile telecommunication system according to clause 22,wherein the message further comprises an indication of one or moresub-pool selection criteria for use by communications devices to selecta sub-pool for transmitting signals.

Clause 24. A mobile telecommunication system according to any of clauses22 to 23, wherein said element is configured to make the determinationbased on an estimated or measured level of collision within the secondresources pool.

Clause 25. A mobile telecommunication system of any of clauses 21 to 24,wherein an indication of one or more sub-pool selection criteria for useby the second communications device to select a sub-pool fortransmitting signals is stored in the second communications device.

Clause 26. A mobile telecommunication system of clause 24 or 25, whereinthe one or more sub-pool selection criteria comprise one or acombination of a reliability level parameter, a communication type, aQuality of Service “QOS” parameter, a latency parameter, a priorityparameter, a throughput parameter, and a maximum number ofcommunications devices in the sub-pool.

Clause 27. A mobile telecommunication system of any of clauses 21 to 26the system further comprising:

an element configured to determine that the level of collision in one ofthe sub-pool is unacceptable based on a comparison with sub-poolacceptability threshold;

wherein the element is configured to, upon determining that the level ofcollision in one of the sub-pool is unacceptable, re-allocate theresources of the second pool between each of the correspondingsub-pools; and

wherein, optionally, the element is one of a base station and acommunications device.

Clause 28. A mobile telecommunication system of any of clauses 19 to 27,the system further comprising:

an element configured to determine that the level of collision in thesecond resources pool is unacceptable based on a comparison with a poolacceptability threshold;

wherein the element is configured to, upon determining that the level ofcollision in the second resources pool is unacceptable, re-allocate theresources between the first and second pools; and

wherein, optionally, the element is one of a base station and acommunications device.

Clause 29. A communications device for device-to-device communication,wherein the communication device is configured to operate in a mobiletelecommunication system, the mobile telecommunication system providinga wireless interface for a base station to communicate withcommunications devices,

wherein the communications device is operable to transmit signals toanother communications device using resources of the wireless interfaceand in accordance with a device-to-device communication protocol;

wherein the communications device being operable to transmit signals inaccordance with a device-to-device communication protocol comprises

-   -   the communications device being operable to transmit broadcast        messages using resources of a first pool of resources; and    -   the communications device being operable to transmit unicast        messages using resources of a second pool of resources, the        second pool of resources being separate from the first pool of        resources.

REFERENCES

-   [1] R2-133840 “CSMA/CA based resource selection,” Samsung, published    at 3GPP TSG-RAN WG2 #84, San Francisco, USA 11-15 Nov. 2013.-   [2] R2-133990, “Network control for Public Safety D2D    Communication”, Orange, Huawei, HiSilicou Telecom Italia, published    at 3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.-   [3] R2-134246, “The Synchronizing Central Node for Out of Coverage    D2D Communication”, feral Dynamics Broadband UK, published at 3GPP    TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.-   [4] R2-134426, “Medium Access for D2D communication”, LG Electronics    Inc, published at 3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15    Nov. 2013.-   [5] R2-134238, “D2D Scheduling Procedure”, Ericsson, published at    3GPP TSG-RAN WG2 #84, San Francisco, USA, 11-15 Nov. 2013.-   [6] R2-134248, “Possible mechanisms for resource selection in    connectionless D2D voice communication”, General Dynamics Broadband    UK, published at 3GPP TSG-RAN WG2 #84. San Francisco, USA, 11-15    Nov. 2013.-   [7] R2-134431, “Simulation results for D2D voice services using    connectionless approach”, General Dynamics Broadband UK, published    at 3GPP TSG-RAN WG2 #84 San Francisco, USA, 11-15 Nov. 2013.-   [8] “D2D Resource Allocation under the Control of BS”, Xiaogang R.    et al, University of Electronic Science and Technology of China,    https://mentor.ieee.org/802.16/dcn/13/16-13-0123-02-000n-d2d-resource-allocation-under-the-control-of-bsdocx-   [9] US20130170387-   [10] US20120300602-   [11] LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Harris    Holma and Antti Toskala, Wiley 2009 ISBN 978-0-470-99401-6.

The invention claimed is:
 1. A communications device configured tocommunicate with another communications device using resources of awireless interface provided by a wireless communications network inaccordance with a device-to-device (D2D) communication protocol, thecommunications device comprising: circuitry configured to selectresources from a first pool of resources allocated for transmitting D2Dbroadcast messages; transmit broadcast messages using the selectedresources of the first pool of resources; select resources from a secondpool of resources allocated for transmitting D2D unicast messages; andtransmit unicast messages using the selected resources of the secondpool of resources.
 2. The communications device of claim 1, wherein thecircuitry is configured to receive, from the wireless communicationsnetwork, a message comprising an indication of a position of the firstpool of resources and a position of the second pool of resources.
 3. Thecommunications device of claim 1, wherein the second pool of resourcesis divided into at least a first sub-pool and a second sub-pool, thefirst sub-pool and the second sub-pool being separate from each other.4. The communications device of claim 3, wherein the circuitry isconfigured to select resources from one of the at least first sub-pooland the second sub-pool for transmitting the unicast messages.
 5. Thecommunications device of claim 3, wherein the circuitry is configured toreceive a message from the wireless communications network indicating aposition of the first sub-pool and a position of the second sub-pool. 6.The communications device of claim 5, wherein the message furthercomprises an indication of one or more sub-pool selection criteria foruse by communications devices to select a sub-pool for transmittingsignals.
 7. The communications device of claim 1, wherein the first poolof resources corresponds to at least a first frequency subcarrier, andthe second pool of resources corresponds to at least a second frequencysubcarrier.
 8. The communications device of claim 7, wherein the firstfrequency subcarrier is different from the second frequency subcarrier.9. The communications device of claim 1, wherein the first pool ofresources corresponds to a first plurality of frequency subcarrier, andthe second pool of resources corresponds to a second plurality offrequency subcarriers.
 10. The communications device of claim 9, whereinthe first plurality of frequency subcarriers is different from thesecond plurality of frequency subcarriers.
 11. The communications deviceof claim 1, wherein the first pool of resources corresponds at least afirst group of resource blocks, and the second pool of resourcescorresponds to a second group of resource blocks.
 12. The communicationsdevice of claim 11, wherein the first group of resource blocks isdifferent from the second group of resource blocks.
 13. Thecommunications device of claim 1, wherein the circuitry is configuredto: receive D2D broadcast messages transmitted from anothercommunications device in resources included in the first pool orresources; and receive D2D unicast messages transmitted from anothercommunications device in resources included in the second pool ofresources.
 14. A user equipment configured to communicate with anothercommunications device using resources of a wireless interface providedby a wireless communications network in accordance with adevice-to-device (D2D) communication protocol, the communications devicecomprising: circuitry configured to receive, from the wirelesscommunications network, a message identifying a first pool of resourcesfor transmitting a broadcast D2D message and a second pool of resourcesfor transmitting a unicast D2D message; select resources from the firstpool of resources for transmitting a D2D broadcast message; transmit abroadcast D2D message using the selected resources of the first pool ofresources; select resources from the second pool of resources fortransmitting a D2D unicast message; and transmit a D2D unicast messageof the second type using the selected resources of the second pool ofresources.
 15. The user equipment of claim 14, wherein the first pool ofresources corresponds to at least a first frequency subcarrier, and thesecond pool of resources corresponds to at least a second frequencysubcarrier.
 16. The user equipment of claim 14, wherein the first poolof resources corresponds to a first plurality of system resource blocks,and the second pool of resources corresponds to a second plurality ofsystem resource blocks.
 17. Circuitry configured for use in a userequipment configured to communicate with another communications deviceusing resources of a wireless interface provided by a wirelesscommunications network in accordance with a device-to-device (D2D)communication protocol, the circuitry configured to: receive, from thewireless communications network, a message identifying a firstallocation of resources for transmitting a D2D broadcast message and asecond allocation of resources for transmitting a D2D unicast message;transmit a D2D broadcast message using resources selected from the firstallocation of resources; and transmit a D2D unicast message usingresources selected from the second allocation of resources.
 18. Thecircuitry of claim 17, wherein the first allocation of resourcescorresponds to a first plurality of system resource blocks, and thesecond allocation of resources corresponds to a second plurality ofsystem resource blocks.